The invention relates to a knitted textile structure comprising metal fibre bundles and into which a reinforcing multifilament insert yarn is incorporated.
Knitted structures comprising metal fibre bundles are described in the PCT patent application WO 97/04152 of the applicant and are being utilized in various fields of application.
These knitted fabrics are fairly heavy as a result of the high specific gravity of the stainless steel fibres of which they are constructed. This is certainly the case when the knitted fabrics are reinforced with an insert yarn which is of the same type as the knitted yarn. The high own weight of these knitted fabrics themselves can result in a certain sagging down when they are used as a covering for various supports. This means that the knitted fabrics do not always remain in an equally close fitting position to the contact-forming (more or less horizontal) supports. For certain applications, this constitutes a significant drawback.
Incorporating a conventional, relatively thick insert yam necessarily results in a knitted fabric with relatively large stitches. For many applications, however, there is a need for a knitted structure with small stitches and reinforced with an insert. But this requires high gauges during knitting, which is not possible if a conventional insert yam is incorporated into the knitted structure. Moreover, during the production of such a reinforced knitted fabric there is a real possibility of knitting defects and damage to the knitting machine.
It is an object of the invention to provide a reinforced, relatively light and thin knitted textile structure that comprises metal fibre bundles and that manages to avoid the drawbacks of the conventionally reinforced metal knitted fabrics described above.
In particular, the invention provides for a single-bed weft-knitted textile comprising stainless steel fibre bundles in which a reinforcing multifilament insert yarn with a titre of less than 180 Tex is incorporated into the textile structure in a regular pattern, e.g. by means of tuck stitches.
The metal fibres (e.g., made of a type of steel from the AISI 300 or 400 series, Fecralloy(copyright), Aluchrome(copyright) or Nicralloy(copyright) which are used in the textile structure according to the invention can be obtained by shaving the edge of a roll of foil as described in U.S. pat. No. 4,930,199, or by means of the technique of bundled drawing, such as described for example in U.S. Pat. No. 3,379,000. The metal fibres have an equivalent diameter which is understood to be between 2 and 100 xcexcm, and by preference between 2 and 40 xcexcm. The equivalent diameter is defined here as the diameter surface area as that of the actual fibre in question.
The multifilament insert yam that is incorporated into the knitted textile structure according to the invention can be a multifilament metal or glass yarn consisting of between 30 and 1500 filaments.
Thus, for example, the insert yarn can be Bekinox(copyright) VN continuous yarn, which is composed of between 70 and 300 stainless steel filaments having an equivalent diameter of between 2 and 30 xcexcm. The portion by weight of the insert in the textile structure is typically less than 35%.
In another embodiment, a multifilament glass fibre insert yam can be incorporated into the textile structure which, for example, is composed of E- or C-type glass fibres with a diameter of between 7 and 9 xcexcm. On average, such glass yams comprise from 30 to 150 filaments. Thus there is a multifilament glass fibre yarn consisting, for example, of 2 single yarns, each containing 22 C-glass filaments that have a diameter of 7 xcexcm and are twisted around one another. The portion by weight of the insert yarn in the textile structure is less than 25%.
The previously mentioned problem of sagging of the textile structure is thus solved by the use of a relatively light insert yarn, which results in a knitted fabric that is lighter in weight and which limits the elasticity of the textile structure in the weft direction. This is a very favourable factor for many applications, including the use of the textile structure as a covering for support structures that are used in the process of shaping or forming glass plates, such as car windows, as will be explained below.
Moreover, a multifilament insert yarn is stronger that a conventional spun insert yarn of the same thickness, so that with a thinner insert yarn a knitted fabric can be obtained which is at least equally strong.
In addition, a thinner insert yarn hinders the stitch formation process to a lesser extent so that with the same gauges a finer knitted fabric (with smaller stitches) can be obtained as compared to the corresponding conventional reinforced product. Moreover, a thinner insert yarn (with tuck stitches) makes it possible to produce reinforced Knitted fabrics with higher gauges than is conventionally possible.
The weft-knitted structure according to the invention is either flat or circularly knitted and is flexible. The textile structure has a weight which is between 600 and 2000 g/m2. Its air permeability is more than 400 L/dm2/min with a pressure drop of 100 Pa.